1. Field of the Invention
The present invention relates to a transponder for tire, a tire with a transponder and a mounting method of the tire with transponder, and more particularly to embedding, into the tire, of the transponder equipped with a sensor for detecting physical quantity in the atmosphere within the tire air chamber.
2. Description of the Related Art
Conventionally, when identification information concerning the tire and other additional information are acquired or information on pneumatic pressure, temperature or the like in the atmosphere within the tire air chamber is acquired, there is known a method of fitting a transponder within the tire to acquire the information without making contact with the tire. Also, the transponder is composed of an integrated circuit and a housing for protecting the integrated circuit, and has various shapes such as a small coin shape or a cylindrical column shape.
An example of technique of this sort is disclosed in Japanese Patent Laid-Open No. 5-169931 specification (first conventional example). According to this technique, an entire housing for the transponder is completely embedded within the tire such that a coil antenna of the transponder having a pressure sensor can be combined with bead wire of the tire. Further, the bead wire is used as the primary winding and the coil antenna is used as the secondary winding. Thereby, the pneumatic pressure within the tire air chamber is detected through the inner wall of the tire, and this detection result is transmitted by wireless.
Also, as another example, a tire with transponder has been disclosed in Japanese Patent Laid-Open No. 11-278021 specification (second conventional example). This tire is provided with fitting structure for fitting the transponder to the inner liner, and after tire vulcanization, the transponder is fitted to the fitting structure.
However, the above described tire with transponder according to the conventional example had the following problems. That is, in the first conventional example, since the pneumatic pressure within the tire air chamber has been detected through the inner wall of the tire, it was necessary to adjust the pressure sensor after the transponder is fitted to the tire. Further, on the inner wall of the tire, pressure or the like which occur by deformation of the inner wall during traveling are also added in addition to the pneumatic pressure within the tire air chamber, and the pressure within the tire air chamber is diffused in the inner wall. Therefore, it was difficult to detect accurate pneumatic pressure within the air chamber.
Also, in the second conventional example, since the transponder is fitted to the fitting structure provided for the inner liner, communication with the interior of the tire air chamber can be secured even if the transponder is provided with a sensor. In the case, however, where the transponder is caused to store tire identification information or other additional information concerning the tire and is made possible to read out, the reliability of the information stored in the transponder is exceedingly low because the transponder can be easily replaced. In other words, it is possible to easily replace with a transponder fitted to another tire, and this is unsuitable structure when information on individual tires is caused to be stored.
Also, there has also been known a transponder constructed such that a communicating tube extending from within the tire air chamber to the outside of the air chamber is provided to couple to the sensor, but since the communicating tube having high strength is required, there was a problem that the weight is increased.
The present invention has been achieved in views of the above described problems, and is aimed to provide a transponder for tire, in which the physical quantity in the atmosphere within the tire air chamber can be accurately detected by a sensor and which can be vulcanized in a state in which it is embedded within the tire, a tire with the transponder, and a manufacturing method of the tire.
According to a manufacturing method of a tire with transponder of the present invention, in order to attain the above described object, there is used a transponder obtained by hermetically sealing and housing a sensor and wireless communication means which constitute an electrical circuit for the transponder, in the space within the housing. This transponder is embedded in the inner wall of a green tire before vulcanization and the green tire is vulcanized. Further, after the vulcanization, a portion of the transponder housing is removed together with a portion of the inner wall surface of the tire to thereby cause the interior of the tire air chamber and space within the transponder housing to communicate with each other.
According to the manufacturing method of a tire with transponder of the present invention, when the green tire with the transponder embedded therein is vulcanized, heat during the vulcanization is applied to the sensor and the wireless communication means through the housing, but the pressure during the vulcanization is interrupted by the housing because the sensor and the wireless communication means are hermetically sealed and housed with in the housing. For this reason, there is no possibility that the pressure during the vulcanization is applied to the sensor and the wireless communication means. Thus, the sensor and the wireless communication means are protected against deterioration and destruction due to the pressure during the vulcanization.
After the green tire is vulcanized, a portion of the transponder housing is removed together with a portion of the inner wall surface of the tire to thereby cause the interior of the tire air chamber and space within the transponder housing to communicate with each other. Thus, since the atmosphere within the tire air chamber enters space within the transponder housing, the sensor within the housing is capable of sensing physical quantity in this atmosphere.
Also, in a process for embedding the transponder, the transponder housing is embedded between the tire inner liner and the carcass ply, whereby the interior of the tire air chamber and space within the transponder housing will be communicated with each other if a portion of the transponder housing is removed together with a portion of the tire inner liner. At this time, a member having light permeability is used as the tire inner liner and the transponder is embedded between the tire inner liner and the carcass ply, whereby the embedded position of the transponder can be easily specified after the vulcanization. Thus, the operation for communicating the space within the transponder housing with the interior of the tire air chamber can be easily performed.
In the process for embedding the transponder, a seat member can be stuck on the tire inner liner so as to cover the transponder housing with the seat member for embedding the transponder on the inner wall of the green tire. Also at this time, a seat member having light permeability is similarly used, whereby the embedded position of the transponder can be easily specified after the vulcanization. Also, by using a seat member having color different from that of the tire inner liner, the embedded position of the transponder can be easily specified after the vulcanization.
In the process for embedding the transponder, the transponder is embedded such that a portion targeted for removal of the transponoder housing is located inside the tire air chamber, whereby an operation for communicating the space within the transponder housing with the interior of the tire air chamber can be further easily performed.
Also, in the present invention, a transponder for tire suitable for the above described manufacturing method of the present invention has been constructed. The transponder for tire according to the present invention has a housing for hermetically sealing and housing the sensor and the wireless communication means. Further, the transponder housing has a portion targeted for removal at a predetermined position, and has space for communicating with a physical quantity sensing unit of the sensor inside the portion targeted for removal.
In the transponder for tire according to the present invention, since the sensor and the wireless communication means are hermetically sealed and housed within the housing, heat during the vulcanization is applied to the sensor and the wireless communication means through the housing, but the pressure during the vulcanization is interrupted by the housing. For this reason, there is no possibility that the pressure during the vulcanization is applied to the sensor and the wireless communication means. Thus, the sensor and the wireless communication means are protected against deterioration and destruction due to the pressure during the vulcanization. Also, after the termination of the vulcanization, the portion targeted for removal of the housing is removed from the tire inner wall side together with the tire inner wall by means of machining, cutting or the like, whereby the space within the housing for communicating with the physical quantity sensing unit of the sensor communicates with the interior of the tire air chamber. Thus, the atmosphere within the tire air chamber enters space within the housing, and physical quantity in this atmosphere the sensor is sensed by the physical quantity sensing unit of the sensor. For example, a pneumatic sensor is proved as a sensor, whereby the pneumatic pressure within the tire air chamber is sensed and this pneumatic pressure information can be transmitted to the main device by wireless communication using an electromagnetic wave or the like.
In the present invention, a semiconductor piezo-resistance type diaphragm is used as a pneumatic sensor, whereby a high degree of reliability has been obtained. More specifically, since such a semiconductor pressure sensor has small mechanical movement of the pressure sensing unit, it is difficult to be affected by a centrifugal force that occurs during rotation of the tire, and accurate pneumatic pressure can be detected. Further, for the semiconductor diaphragm, a capacity type and a film type are generally known in addition to the piezo-resistance type, but the capacity type diaphragm is prone to be affected by electromagnetic wave noise, and the film type diaphragm is hardly reliable because complicated in structure. The semiconductor piezo-resistance type diaphragm is more highly reliable than these capacity type and film type.
In the present invention, the transponder housing has been shaped to have a protruded portion for protruding from the main body of the housing. Further, in this housing, the space within the housing is continuously formed within the protruded portion. If the protruded portion of the housing is embedded in the inner wall of the tire so as to be able to be identified or easily removed, the whole protruded portion or a portion thereof is removed together with a portion of the inner wall from the inner wall side of the tire, whereby the space within the housing can be easily communicated with the interior of the tire air chamber.
Also, in the transponder according to the present invention, the wireless communication means is isolated from space within the housing which is communicated with the interior of the tire air chamber so as to prevent the atmosphere within the tire air chamber from being directly applied to the wireless communication means, whereby the wireless communication means has been prevented from being deteriorated. Further, in the present invention, the transponder housing is made of bisphenol A epoxy resin, whereby strength withstanding the vulcanization has been given. Also, since an electromagnetic wave permeates the bisphenol A epoxy resin, the electromagnetic wave can be restrained from attenuation even if the transponder is equipped with wireless communication means which communicates through the electromagnetic wave.
Also, the transponder for tire according to the present invention has storage means in which identification information peculiar to individual transponders has been stored, and transmits an answering signal including identification information. For this reason, the individual transponders can be identified through the use of the identification information. Further, in the present invention, there has been constructed a transponder for tire in which the additional information is caused to be stored in the storage means in advance in addition to the identification information and which transmits an answering signal including the identification information and additional information. For this reason, as the additional information, information concerning the transponder and information concerning a tire to which the transponder has been fitted are caused to be stored in the storage means in advance, whereby this additional information can be held by the tire itself. Further, according to the present invention, the structure has been arranged such that the additional information can be renewed from the main device by wireless.
As regards a tire with transponder according to the present invention which has been manufactured in accordance with the manufacturing method of the present invention through the use of the above described transponder for tire of the present invention, since the transponder housing is embedded in a green tire before vulcanization, it becomes impossible to take the transponder out of the completed tire after the vulcanization leaving no traces. In other words, in order to replace the transponder, the transponder housing must be dug out of the tire inner wall. For this reason, when the transporter embedded in the tire inner wall is replaced, the traces of this replacement operation can be easily recognized by visual inspection and the traces of the replacement remain clearly. This enables the reliability of information such as history of the tire stored in the transponder to be increased. Further, the interior of the tire air chamber and the physical quantity sensing unit of the sensor communicate with each other through the aperture of the transponder housing, and therefore, the sensor is capable of directly sensing the physical quantity in the atmosphere within the tire air chamber, and detecting accurate physical quantity.